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POLYPODY.
P o l y p o d iu m V u l g ä r e of Authors.
LOCALITIES.
E n g la n d .
Wa l e s .
Scotland.
I r e l a n d .
Universally distributed.
T h e genus Polypodium is another of those immense groups
which require rigid investigation and careful subdivision. The
species are universally distributed: generally speaking, they are
not remarkable for beauty of appearance, hut they are so various
in figure and habit that no general observation can be strictly
apphed to them.
The common Polypody is one of our best known and most
abundant ferns; it is to he found in almost every hedge. I t
abounds on stone walls, and on the surface of weather-beaten
rocks, quickly succeeding the mosses and lichens which first
establish a footing in these situations.
JiNii
The roots are brown, and often clothed with a thick pilosity.
The rhizoma is brown, and entirely covered with a densely
pilose cuticle, which dries and peels off after one year’s growth,
leaving the rhizoma smooth ; it is decidedly creeping, making
annual advances of great extent. The young fronds are thrown
out in May and June ; they arrive at maturity early in September,
and retain their full vigour until the fronds of the
succeeding year make their appearance. The young fronds are
generally erect at first, but droop by degrees, and are always
pendent when mature : the rachis is green ; more than one-third
of its length is perfectly naked ; the form of the frond is strapshaped
and pinnatifid, and acute at the apex ; the pinnæ are
nearly linear, and rounded at the apex ; their margins are more
or less serrated. The usual size is shewn in the detached
pinnulæ, represented in the preceding page. The fronds are
fertile only, but the thecæ are generally confined to its upper
part : when without fruit the imperfection arises from uncongenial
situation, and the plant is not to he considered in a
perfectly natural and healthy state.
The situation of the veins is shown in a detached pinnula
(see the preceding page): the lateral veins are alternate, and
each is divided into four branches, three of which extend nearly
to the margin, and are incrassated at their termination; the
fourth is directed forwards, and its termination, which is nearly
equidistant from the midvein and margin, bears a circular
mass of thecæ, which is entirely without indusium ; a single
lateral vein, its four branches, the attachment of the thecæ,
and the extent of the circular mass, indicated by a dotted
line, are shewn in the upper figure, to the light, of the
preceding page.
In form of frond the Common Polypody is very uniform ; it
is however subject to a few variations, some of which are
remarkable; the detached pinnula* to the left, hearing the
masses of thecæ, shows a strongly serrated variety, and the entire
frond to the r ig h tf has the termination of the pinnæ bifid:
another variety, which is perfectly barren, is so strongly serrated,
that Linneus considered it a distinct species, and described it
under the name of Polypodium Cambricum : the identical frond,
named and described by that great naturalist, is now in the
J
See preceding page. t Ib.